test: modernizing test-dgram-listen-after-bind with arrow functions

PR-URL: #23500
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

test/parallel/test-dgram-listen-after-bind.js

@@ -29,16 +29,16 @@ const socket = dgram.createSocket('udp4');
 socket.bind();
 
 let fired = false;
-const timer = setTimeout(function() {
+const timer = setTimeout(() => {
   socket.close();
 }, 100);
 
-socket.on('listening', function() {
+socket.on('listening', () => {
   clearTimeout(timer);
   fired = true;
   socket.close();
 });
 
-socket.on('close', function() {
+socket.on('close', () => {
   assert(fired, 'listening should fire after bind');
 });